Dysbiose

Dysbiose, or dysbiosis, refers to an imbalance in the microbial communities that inhabit the human body, most commonly the intestinal microbiota. It is characterized by reduced microbial diversity, changes in the relative abundance of major bacterial groups, and a loss of beneficial species accompanied by an overgrowth of potentially harmful organisms. While the gut is the most studied site, dysbiosis can occur in other body habitats such as the oral cavity, skin, and vagina. The concept emphasizes shifts in ecological equilibrium rather than a single pathogen.

Causes include antibiotic exposure, infections, and other treatments that perturb the microbiome, as well as dietary patterns (low fiber, high fat or sugar), obesity and metabolic conditions, aging, stress, smoking, and certain medications (for example proton pump inhibitors and nonsteroidal anti-inflammatory drugs). Environmental and genetic factors can modulate susceptibility, and disease processes can both cause and be caused by dysbiosis.

Dysbiosis is associated with a range of conditions. In the gut, it is linked to inflammatory bowel diseases, irritable bowel syndrome, obesity, type 2 diabetes, and metabolic syndrome; in women, vaginal dysbiosis relates to infections; oral and skin dysbioses are connected to periodontal disease and dermatitis. However, causal relationships are complex and context-dependent; dysbiosis can be a consequence of disease rather than a primary cause, or part of a bidirectional interaction.

Diagnosis relies on microbiome analyses, often through sequencing to assess diversity and composition, alongside clinical evaluation. There is no single diagnostic criterion. Management focuses on identifying and addressing underlying causes, promoting a diverse diet rich in plant fibers, prudent use of antibiotics, and, in selected cases, microbiome-directed therapies such as probiotics, prebiotics, or fecal microbiota transplantation.